I would suggest getting your machine oiled, also replace the needle everytime it starts jamming because it could be dull. Finally check your bobbin tension. My mom's machine was jamming and it turned out that I just needed to reset everything back to basic and change out the bobbin and needle. It's been fine ever since.

Yeah, I am always changing tension, never seem to find the right setting. I do need to remember to change needles, I know that they have to be sharp not to jam. But it's getting ridiculous.

My machine is a small portable (White brand) and once, about 20 years ago, a friend got me a job sewing a big curtain for a theater company. It was just a hem job, but it was a huge curtain so I brought my machine and worked on it on the floor. What the theater manager did not tell me is that he was still painting the backdrop on it while I was sewing. I needed the money at the time, so I continued but paint got into my machine and it's never been the same since. I think a general overhaul would do it some good, but sometimes I wonder if just buying a new machine would be a better solution. QVC sometimes sells machines for less than $200. I have no idea how much it would cost to fix this one.